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DNV GL AS
RULES FOR CLASSIFICATION
ShipsEdition October 2015
Amended January 2016
Part 4 Systems and components
Chapter 5 Rotating machinery - driven units
-
FOREWORD
DNV GL rules for classification contain procedural and technical
requirements related to obtainingand retaining a class certificate.
The rules represent all requirements adopted by the Society asbasis
for classification.
© DNV GL AS October 2015
Any comments may be sent by e-mail to [email protected]
If any person suffers loss or damage which is proved to have
been caused by any negligent act or omission of DNV GL, then DNV GL
shallpay compensation to such person for his proved direct loss or
damage. However, the compensation shall not exceed an amount equal
to tentimes the fee charged for the service in question, provided
that the maximum compensation shall never exceed USD 2 million.
In this provision "DNV GL" shall mean DNV GL AS, its direct and
indirect owners as well as all its affiliates, subsidiaries,
directors, officers,employees, agents and any other acting on
behalf of DNV GL.
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CHANGES – CURRENT
This is a new document.The rules enter into force 1 January
2016.
Amendments January 2016
• General— Only editorial corrections have been made.
Editorial correctionsIn addition to the above stated changes,
editorial corrections may have been made.
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CONTENTS
Changes –
current..................................................................................................
3
Section 1
Propellers................................................................................................
81
General................................................................................................
8
1.1
Application.......................................................................................
81.2
Documentation.................................................................................
81.3 Certification
requirements................................................................
10
2
Design................................................................................................122.1
General..........................................................................................122.2
Criteria for propeller blade
dimensions.............................................. 132.3
Pitch control mechanism and propeller
hub........................................ 142.4 Fitting of
propeller blades to the
hub................................................ 16
3 Inspection and
testing.......................................................................163.1
General..........................................................................................163.2
Inspection and testing of
parts.........................................................17
4 Workshop
testing...............................................................................184.1
General..........................................................................................18
5 Control and
monitoring......................................................................185.1
General..........................................................................................18
6
Arrangement......................................................................................196.1
General..........................................................................................196.2
Arrangement of
propeller.................................................................196.3
Hydraulic system for pitch
control.....................................................20
7
Vibration............................................................................................
207.1
General..........................................................................................20
8 Installation
inspection.......................................................................
208.1
General..........................................................................................208.2
Fitting of propeller and propeller
blades.............................................208.3 Pitch
marking.................................................................................
208.4 Hydraulic
piping..............................................................................20
9 Shipboard
testing..............................................................................
219.1 Sea
trial........................................................................................
21
Section 2 Water
jets.............................................................................................
221
General..............................................................................................
22
1.1
Application.....................................................................................
22
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1.2
Documentation...............................................................................
221.3 Certification
requirements................................................................
231.4
Definitions......................................................................................25
2
Design................................................................................................262.1
General..........................................................................................262.2
Design of
components.....................................................................
26
3 Inspection and
testing.......................................................................273.1
General..........................................................................................273.2
Testing and inspection of
parts.........................................................273.3
Assembling.....................................................................................27
4 Workshop
testing...............................................................................284.1
General..........................................................................................28
5 Control, alarm, safety functions and
indications................................285.1
General..........................................................................................285.2
Monitoring and bridge
control...........................................................28
6
Arrangement......................................................................................296.1
General..........................................................................................29
7
Vibration............................................................................................
307.1
General..........................................................................................30
8 Installation
survey.............................................................................308.1
Surveys.........................................................................................
30
9 Shipboard
testing..............................................................................
309.1
General..........................................................................................30
Section 3 Podded and geared
thrusters................................................................
321
General..............................................................................................
32
1.1
Application.....................................................................................
321.2
Definitions......................................................................................321.3
Documentation...............................................................................
331.4 Certification
requirements................................................................
35
2
Design................................................................................................372.1
General..........................................................................................372.2
Shafting.........................................................................................382.3
Gear
transmissions..........................................................................382.4
Azimuth steering gear for
thrusters...................................................382.5
Steering column and pod stay and underwater
housing........................402.6
Propeller........................................................................................
412.7
Bearings........................................................................................
412.8 Lubrication
system..........................................................................41
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3 Inspection and
testing.......................................................................423.1
General..........................................................................................423.2
Assembling.....................................................................................42
4 Workshop
testing...............................................................................424.1
Testing of assembled
unit................................................................
42
5 Control, alarm, safety functions and
indication..................................435.1
General..........................................................................................435.2
Bridge
control.................................................................................44
6
Arrangement......................................................................................456.1
General..........................................................................................456.2
Propulsion
thrusters........................................................................
46
7
Vibration............................................................................................
467.1 Torsional
vibration...........................................................................46
8 Installation
Inspection......................................................................
478.1 Installation
onboard........................................................................
478.2 Install fastening to
foundation..........................................................47
9 Shipboard
testing..............................................................................
479.1 Sea
trial........................................................................................
47
Section 4
Compressors..........................................................................................481
General..............................................................................................
48
1.1
Application.....................................................................................
481.2
Documentation...............................................................................
481.3 Certification
required.......................................................................50
2 Workshop
testing...............................................................................512.1
General..........................................................................................51
3
Design................................................................................................523.1
General..........................................................................................523.2
Piping and
arrangement..................................................................
523.3
Crankshafts....................................................................................
533.4 Rotors for non-reciprocating
compressors.......................................... 553.5 Rotor
casing for non-reciprocating
compressors.................................. 55
4 Control and
monitoring......................................................................554.1
General..........................................................................................55
5 Arrangement
on-board......................................................................
565.1
General..........................................................................................56
6
Vibration............................................................................................
566.1 Torsional
vibration...........................................................................56
7 Installation
inspection.......................................................................
57
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7.1
General..........................................................................................577.2
Vibration........................................................................................
57
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SECTION 1 PROPELLERS
1 General
1.1 Application
1.1.1 The rules in this section apply to propellers intended for
propulsion, steering and manoeuvring, subjectto certification.Ch.2
describes all general requirements for rotating machinery and forms
the basis for all sections in Ch.3,Ch.4 and Ch.5.
1.1.2 The following items are recognised as parts of the
propeller and are subject to approval:
— propeller blades— blade fitting mechanism (e.g. blade bolts -
if any)— propeller hub— pitch control mechanism (if any).
For fitting of the propeller to the shaft, see Ch.4 Sec.1.
1.1.3 See Pt.6 Ch.6 Sec.1 concerning propellers for ships with
ice strengthening.
1.1.4 See Pt.5 Ch.13 concerning additional requirements for
propellers for naval vessels.
1.1.5 See Pt.6 Ch.2 Sec.7 concerning additional requirements
related to redundant propulsion.
1.1.6 See Pt.6 Ch.3 Sec.1 and Pt.6 Ch.3 Sec.2 concerning
additional requirements related to dynamicpositioning systems.
1.2 Documentation
1.2.1 The Builder shall submit the documentation required by
Table 1. The documentation shall be reviewedby the Society as a
part of the class contract.
Table 1 Documentation requirements
Object Documentation type Additional description Info
C020 - Assembly or arrangementdrawing FI
C030 – Detailed drawing
Detailed geometry, including:
— Verification details of fitting of hub topropeller shaft
— Blade fitting arrangement (asapplicable).
Material specification, properties and heattreatment.
AP
C040 – Design analysis Fitting calculation. FI, R
Hub
Z162 - Installation manual Shall follow each delivery. FI, R
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Object Documentation type Additional description Info
C030 - Detailed drawingDetailed geometry, including blade
flange,as applicable. Material specification,properties and heat
treatment.
AP
Blade
C040 – Design analysis
FE calculation (Mandatory for specialdesigns), including
backgrounddocumentation:
— Detailed hydrodynamic calculation— Wake field data.
(Blade geometry data file in ASCII format,preferably PFF may be
requested).
FI, R
Controllable pitch servomechanism C030 - Detailed drawing
Detailed geometry of all load carryingparts, such as actuator
cylinder, pistonand piston rod.Material specification, properties
and heattreatment
AP
S042 - Hydraulic control diagramIncluding permissible operating
servopressures, specification of oil filter, andalarm list with
setpoint and relay times
AP
Z161 - Operation manual If pitch adjustment is used as load
controlof propeller driver. FI, R
C020 - Assembly or arrangementdrawing FI
C030 - Detailed drawing
Detailed geometry of all load carryingparts, such as crank disc,
push pull rod,actuator cylinder, cross head, sliding shoe,hub cap
including fin, and cap bolts.Material specification, properties and
heattreatment
AP
Controllable pitchmechanism
C040 – Design analysisAnalysis including description of
pitchpropeller system is mandatory for newdesign.
FI, R
Control and monitoringsystem
I200 - Control and monitoring systemdocumentation According to
Ch.9 AP
AP = For approval; FI = For information; R = On request
1.2.2 For general requirements for documentation, including
definition of the info codes, see Pt.1 Ch.3 Sec.2.
1.2.3 For a full definition of the documentation types, see Pt.1
Ch.3 Sec.3.
1.2.4 Relevant design parameters shall be given. As a minimum,
the following shall be specified:
— engine power at maximum continuous rating (MCR)— corresponding
propeller rotational speed— maximum ship speed— design pressure of
hydraulic pitch system (if any)— relevant additional class
notations (see [1.1.3]-[1.1.6]).
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The manufacturing tolerance class (ISO 484) shall be specified
on the propeller drawings.
1.2.5 The following additional information shall also be
submitted for the propeller:
— weight and buoyancy— polar and diametrical mass moment of
inertia— predicted operational hydraulic pressure for controllable
pitch propellers, when available.
1.2.6 For instrumentation and automation, including computer
based control and monitoring, see Ch.9.
1.3 Certification requirements
1.3.1 Pumps, electric motors, coolers, piping, filters, valves,
etc. that are delivered as integral parts of thehydraulic operation
and cooling systems, shall be checked as found relevant by the
propeller manufacturer’squality system.
1.3.2 Certificates shall be issued as per Table 2 and scope of
testing and inspection of components as perTable 3.
Table 2 Certification required for propeller
Object Certificatetype Issued byCertificationstandard*
Additional description
PC
MC
NDT (see Pt.2 Ch.2 Sec.7 and Pt.2 Ch.2Sec.10).
Propellers cast in one piece
TR
Society
Dimension control (see [3.1.9])
PC
MC
NDT (see Pt.2 Ch.2 Sec.7 and Pt.2 Ch.2Sec.10).
Separate blades
TR
Society
Dimension control (see [3.1.9])
MC Society PC and MC may be issued bymanufacturer for axillary
propeller
NDT Society (see Pt.2 Ch.2 Sec.7 and Pt.2 Ch.2Sec.10).Separate
hubs
NDT Manufacturer (see Pt.2 Ch.2 Sec.7 and Pt.2 Ch.2Sec.10).
Fixed pitch propeller hub cap TR Manufacturer Material and
dimension control
PC Society PC may be issued by manufacturerfor auxilliary
propeller.
MC ManufacturerBlade bolts
NDT Manufacturer
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Object Certificatetype Issued byCertificationstandard*
Additional description
MC
Crank disc, push pull rod, actuatorcylinder and cross head.Other
parts of pitching mechanismupon request
Controllable pitch mechanism
NDT
ManufacturerNDT shall cover highly stressedareas, such as blade
bolts, crankdisk fillet, threads of push-pullrods, etc.
Pitch control and monitoringsystem PC Society See Ch.9
PC = product certMC = material certTR = test reportTA = Type
approvalNDT = NDT report
*Unless otherwise specified the certification standard is the
Society rules.
1.3.3 For general certification requirements, see Pt.1 Ch.3
Sec.4.
1.3.4 For a definition of the certification types, see Pt.1 Ch.3
Sec.5.
1.3.5 The surveyor shall do visual inspection of parts. Visual
inspection shall include random dimensionalcheck with emphasis on
critical dimensions, tolerances and stress raisers.Manufacturer’s
measurement report shall be presented for main items and shall be
available upon request forminor components.Manufacturer’s survey
report shall be available upon request.
Table 3 Testing and inspection of components
ComponentMaterial test (chemicalcomposition andmechanical
properties)
Magneticparticleinspection ordye penetrant
Visual and dimensionalinspection
Propellers cast in one piece Society Society Society1)
Separate blades Society Society Society1)
Separate hubs Society or Manufacturer2) Manufacturer3) Society
or Manufacturer2)
FPP hub cap Manufacturer
Blade bolts Society or Manufacturer2) Manufacturer
Manufacturer
Crank disc, push pull rod, actuatorcylinder and cross head.
Other partsof pitching mechanism when foundnecessary
Manufacturer Manufacturer4) Manufacturer
The propeller shall be delivered with a Society’s certificate,
see [1.1.1]. Reference is also given to [1.1.2].
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ComponentMaterial test (chemicalcomposition andmechanical
properties)
Magneticparticleinspection ordye penetrant
Visual and dimensionalinspection
1) See also [3.1.9]2) The Society if propulsion.3) Only required
in A and C zones (see Pt.2 Ch.2 Sec.8 and Pt.2 Ch.2 Sec.11 [3]).4)
Only required in highly stressed areas, such as blade bolts, crank
disk fillet, threads of push-pull rods, etc.
2 Design
2.1 General
2.1.1 Materials for propellers shall comply with the
requirements in Pt.2 Ch.1 and Pt.2 Ch.2.For other materials,
particulars of mechanical properties and chemical compositions
shall be submitted tothe Society. Fatigue properties different from
the ones given in Table 4 may be accepted, provided
sufficientdocumentation is presented.
Table 4 Material properties
MaterialMaterial constant
U1 (N/mm2)
Material constantU2 (-)
Minimum yield strengthσy (N/mm
2)Minimum tensile strength
σB (N/mm2)
Mn-Bronze, CU1(High tensile brass)
55 0.15 175 440
Mn-Ni-Bronze, CU2(High tensile brass)
55 0.15 175 520
Ni-Al-Bronze, CU3 80 0.18 245 590
Mn-Al-Bronze, CU4 75 0.18 275 630
Martensitic stainless steel(12Cr 1Ni)
60 0.20 440 590
Martensitic stainless steel(13Cr 4Ni/13Cr 6Ni)
65 0.20 550 750
Martensitic stainless steel(16Cr 5Ni)
70 0.20 540 760
Austenitic stainless steel(19Cr 10Ni)
55 0.23 180 440
Forged steel and other materials shall be especially
considered.
Guidance note:Fatigue properties in sea water U1 (fatigue
strength amplitude) and U2 (relative reduction of fatigue strength
with increasing meanstress) may be documented in accordance with
the following recommended testing procedure:
— Material specimen without notches should be tested in “sea
water”. The specimen should be welded, according to an
approvedrepair method, including post heat treatment as applicable.
Surface roughness should be as for finished propellers.
Materialproperties and chemical composition should be
representative for the minimum material requirements.
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— Bending of flat bars is preferred, but testing with rotating
bending is also acceptable.
— Thickness of specimen should be at least 25 mm.
— Number of cycles to be at least 107 at a bending frequency not
higher than 5 Hz.
— Number of tests should be minimum 25. Specimen shall be taken
from at least two separate material charges.
— Testing should be performed according to the “Staircase
method”.
U1 (N/mm2) to be taken as:
Where:
UE7= average fatigue amplitude (N/mm2), corresponding to 107
cycles at zero mean stress (stress ratio, R = -1)σE7= corresponding
standard deviation (N/mm2).
The factor of 1.3 reflects a correction related to tested number
of cycles vs. the expected number of cycles experienced during
aships life time.The factor of 2.0 is chosen to account for the
scatter of fatigue strength.In case U2 should be documented,
additional testing should be carried out as above, with a stress
ratio, R = 0.
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2.1.2 The requirements given in [2.2], [2.3], and [2.4] apply to
all propellers of conventional design andarrangement, unless
otherwise explicitly stated. For propellers not recognised as
conventional by the Society(e.g. surface piercing propellers, tip
fin propellers, cycloidal propellers etc.), the approval shall be
based onspecial consideration.
2.1.3 The combination of materials shall be such as to minimise
galvanic corrosion.
2.1.4 The surface of the hub, conical bores, fillets and blades
shall be smoothly finished.
2.2 Criteria for propeller blade dimensions
2.2.1 The following load conditions shall be considered:
a) High cycle dynamic stresses (> 108 cycles) due to
rotational propeller load variation in normal, aheadoperation.
b) Low cycle dynamic stresses (< 106 cycles) due to propeller
load variations in a seaway, manoeuvres,starting and stopping,
reversing, repetitive ice shock loads etc. shall also be considered
when dynamicstresses are not dominated by high cycle load
variations, e.g. for propellers for which turning directionmay be
reversed and propellers running in undisturbed axial inflow.
Guidance note:Class Guideline DNVGL-CG-0039 offers detailed
methods on how to assess the minimum safety factors in Table 5 for
these loadconditions.Alternative methods may also be considered on
the basis of equivalence.
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2.2.2 The propeller blades shall be designed with the minimum
safety factors as given in Table 5, seealso guidance note in
[2.2.1]. The safety factors reflect the expected inaccuracies in
the methods used forpredictions of loads and stress calculations,
as well as the influence of allowable material defects.It is on the
condition that manufacturing tolerance class I or S is specified
according to ISO484 for propulsionpropellers. (Tolerance class II
or better for other propellers.)Otherwise higher safety factors may
be required, based upon special consideration.
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Table 5 Minimum safety factors for propeller blades
Load conditionApplication Considered Section
Static Low cycle fatigue High cycle fatigue
At root section - - 1.8All propellers, exclusive tunnel
thrusters
At 0.6R - - 1.6
Reversible direction of rotation,exclusive tunnel thrusters At
0.8R - 1.5 -
Tunnel thrusters At root section 2.2 - -
2.2.3 Somewhat lower safety factors than given in Table 5 may be
accepted after special consideration ifdynamic stresses are
documented by means of reliable measurements and/or advanced
calculation method.
2.2.4 Blade root fillet shall be designed in order to maintain a
safety factor in the fillet as required for theroot section.
Fillets with constant radius of 75% of root thickness, or
multi-radius fillets of a “constant stress”design are considered to
comply with this requirement.
2.2.5 For calculation of the blade stress of special propeller
designs such as tip fin propellers, special profiles,etc., FE
calculation shall be submitted with documented details of the
hydrodynamic loads.For calculation of the blade stress of these
special propeller designs, in addition to the documents to
besubmitted according to [1.2], a blade geometry data file (ASCII
format, preferably PFF) shall be submitted tothe Society.
Supplementary information for propellers of special designs can be
requested by the Society.
2.2.6 If the propeller is subjected to an essential wear e.g. by
abrasion in tidal flats or dredgers, a wearaddition shall be
provided to the thickness determined according to class
requirements to achieve anequivalent lifetime.
2.2.7 If the propeller of azimuthing thruster is subjected to
highly oblique inflow in transient conditions suchas crash stop
manoeuvring, the propeller blade shall be strengthened
accordingly.
2.2.8 Regarding devices for improving propulsion efficiency, the
rules for classification of ships Pt.3 Hull, hasto be observed.
2.3 Pitch control mechanism and propeller hub
2.3.1 Mechanical components of a pitch control system and
propeller hub shall be able to withstand thestatic loads with the
safety factor against yield as specified in Table 6.
Table 6 Minimum safety factors for static strength of propeller
hub, pitch mechanism and bladefitting mechanism
Load condition Required safety factor
Load transmitted when two of the blades are prevented from
pitching (servo force acting ontwo blades) 1.0
Load transmitted when a propeller blade is exposed to maximum
hydrodynamic load 2.0
Load corresponding to maximum servo pressure for strengthening
the hub cap 2.0
Load corresponding to maximum servo pressure, with the load
evenly distributed on allblades 1.3
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Guidance note:The latter load case is dimensioning for push-pull
rods.
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2.3.2 Safety factors for static load conditions reflect the risk
and criticality related to the specified loadconditions, as well as
the expected prediction quality of the acting loads. The minimum
safety factors shallbe against yielding, and shall be applied on
acting load. Local geometrical stress concentrations may
beneglected. Stresses referred to are equivalent stresses. It is
provided that stresses are predicted according togood engineering
practice.
2.3.3 Maximum servo force (servo pressure corresponding to set
point to safety valve) shall be applied in thecalculations. Guide
pin is assumed to be located in the most critical position.
2.3.4 Unless the propeller is intended for auxiliary purposes
only, fatigue strength of pitch mechanism andpropeller hub shall be
considered taking the load conditions specified in Table 7 into
account:
Table 7 Minimum safety factors for fatigue strength of propeller
hub and pitch mechanism
Load condition Required safety factor
Start and stop of propeller 1.5
Change of pitch setting in normal operating condition 1.5
Rotational load variation of propeller in normal, ahead
operation (for propellersintended for propulsion only). 1.5
2.3.5 Fatigue strength related to each load condition can be
calculated separately.
2.3.6 Number of cycles shall correspond to a realistic number of
load variations, corresponding to thedescribed condition.
2.3.7 Safety factors for dynamic load conditions reflect the
risk and criticality related to the specified loadconditions, as
well as the expected prediction quality of the acting loads and
fatigue strength of material.Safety factor shall be applied on
acting dynamic load vs. fatigue strength of material. Influence of
stressconcentrations shall be taken into account in fatigue
calculation. Stresses referred to shall be principalstresses. It is
presumed that stresses and fatigue strength are predicted according
to good engineeringpractice.
Guidance note:Class Guideline DNVGL-CG-0039 offers more
information on how to assess the minimum safety factors in Table 5
for these loadconditions.Alternative methods may also be considered
on the basis of equivalence.
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2.3.8 The design shall be such that reasonably low stress
concentrations are ensured.
2.3.9 For shrink fitted propellers, hub thickness shall be
sufficient to avoid stresses from the dynamic loadingof propeller
blades influencing significantly on the shrink fit and vice
versa.
Guidance note:In order to provide the above statement a hub
thickness in way of propeller blade corresponding to 70% of the
required thicknessof the propeller blade root section is considered
enough as a minimum.
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2.3.10 The degree of filtration of hydraulic oil shall
correspond to maximum allowable particle size in thesystem or
better. In addition, the selection and arrangement of filters shall
provide for an uninterruptedsupply with filtered oil, also during
filter cleaning or exchange.
Guidance note:Specification of a pressure filter for maintaining
suitable fluid cleanliness may be 16/14/11 according to ISO
4406:1999 and β6-7(c) = 200 according to ISO 16889:2008.
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2.3.11 For general design requirements for piping and ancillary
equipment such as pipes, pumps, filters andcoolers see Ch.6 and
Ch.7, as found applicable.
2.3.12 The boss cap shall have sufficient strength to protect
the shaft end effectively from water ingress. Iffins are mounted
any damage of the fins shall not harm the integrity of the cap.
Guidance note:The boss cap should be thicker than the fin.
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2.4 Fitting of propeller blades to the hub
2.4.1 The pre-tensioning of the blade bolts shall ensure
friction forces sufficient to prevent sliding of thepropeller
flange with a safety factor greater than 1.0 when the propeller is
exposed to forces as described inTable 6 If shear pins are fitted,
the sum of friction and shear forces shall be considered. The blade
retainingbolts shall be tightened in a controlled way to ensure an
appropriate pretension. Pretension stress in theminimum section of
the blade bolts shall be in the range of 50 to 70% of the
bolt-material yield strength ormaximum 56% of the tensile strength,
whichever is the least. During operation any blade opening or loss
ofbolt pretension shall be prevented. The blade bolt stress shall
not exceed yield strength of the bolt material.
2.4.2 The blade bolt pre-stress shall be high enough to ensure
that a certain minimum surface pressurebetween mating surfaces is
obtained in all permissible operating conditions.
2.4.3 High cycle dynamic stress amplitudes in the minimum thread
section of the blade bolts for propellersintended for propulsion
shall fulfil the following criterion:
S = safety factor, not to be less than 1.5σA = dynamic stress
amplitudeU = allowable nominal stress amplitude in the threaded
area, 35 N/mm2 for machined threads and 60
N/mm2 for rolled threads.
2.4.4 Other means of propeller blade fitting mechanisms shall be
especially considered.
3 Inspection and testing
3.1 General
3.1.1 Blade bolt pre-tensioning shall be carried out in the
presence of a surveyor.
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3.1.2 All tests and inspections in [3.1.4] to [3.1.7] shall be
carried out in the presence of a surveyor.
3.1.3 For controllable pitch propellers, all connections shall
be properly sealed.
3.1.4 For controllable pitch propellers intended for propulsion,
the following pitch settings shall, as aminimum, be properly marked
on the hub and blade flange:
— pitch at 70% radius is zero— maximum pitch ahead (pitch
limited by mechanical pitch stopper)— maximum pitch astern (pitch
limited by mechanical pitch stopper)
The correctness of pitch marks and the mechanical feedback of
pitch setting shall be verified by the Society.
3.1.5 The function of the pitch stoppers shall be demonstrated.
If pitch stoppers are located outside of thehub, it shall be
verified by the Society that maximum travel in each direction is
less than inside the propellerhub.
3.1.6 After assembly, the complete servo system shall be
properly flushed.
3.1.7 The complete controllable pitch propeller system shall be
function tested and pressure tested asfollows:
— hydraulic pitch control to 1.5 times design pressure—
tightness of propeller subject to 1 bar.
3.1.8 The tightness test for FPP hub cap shall be carried
out.
3.1.9 The propeller blades shall be manufactured according to
the specified tolerance class (ISO 484).As a minimum, verification
of the following is required:
— surface finish— pitch (local and mean pitch)— thickness and
length of blade sections— form of blade sections— location of
blades, reference line and blade contour— balancing (see also
[4.1])— for propellers running in nozzle or tunnel:
— extreme radius of blades (for controllable pitch propellers
with outer section at zero pitch).
See also [2.1.4].For verification of blade edge thickness for
ice classed propellers, see also: Pt.6 Ch.6.
Guidance note:Verification of blade section form may include the
use of edge templates as specified for manufacturing tolerance
classes S and Iin ISO 484.Equivalent methods can be accepted, for
instance the use of multi-axial milling machines, which have proven
to be capable ofproducing the specified geometry with such an
accuracy that only a slight grinding is necessary to obtain the
specified surface finish.
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3.2 Inspection and testing of parts
3.2.1 Certificates shall be provided as required in Table 2.
3.2.2 With respect to non-destructive testing for detection of
surface defects, the following acceptancecriteria apply:
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— for propeller blades and hubs, the criteria given in Pt.2 Ch.2
Sec.8 and Pt.2 Ch.2 Sec.11 apply— no defects are accepted in highly
stressed areas of components in the pitching mechanism.
4 Workshop testing
4.1 General
4.1.1 The complete propeller shall be statically balanced in
accordance with specified ISO 484 tolerance class(or equivalent) in
presence of a surveyor. Dynamic balancing shall be carried out for
propulsion propellerswith tip speed exceeding 60 m/s. The
manufacturer shall demonstrate that the assembled propeller shall
bewithin the specified limits.
Guidance note:For built-up propellers, the required static
balancing may be replaced by an individual control of blade weight
and gravity centreposition.
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5 Control and monitoring
5.1 General
5.1.1 For controllable pitch propellers, control and monitoring
systems shall comply with the requirements ofCh.9.
5.1.2 Pitch adjustment shall not be used as load control system
of prime mover, unless the propeller systemis especially designed
for this purpose.
5.1.3 A local control stand for pitch control shall be
arranged.
5.1.4 Instrumentation and alarms shall be provided according to
Table 8, if not otherwise approved.
Table 8 Control and monitoring of propeller
System/Item
Gr 1Indication
alarm
load reduction
Gr 2Automatic
start ofstandby pump
with alarm
Gr 3Shutdownwith alarm
Comments
1.0 Pitch, speed and direction of rotation
Propeller rotational speed IR
Direction of rotation forreversible propellers IR
Propeller pitch for CP-propellers IL, IR
For propulsion, the following pitchsettings shall be marked on
the localpitch indicator:
— Mechanical pitch limits aheadand astern, pitch at full
aheadrunning, maximum astern pitchand pitch at zero thrust.
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System/Item
Gr 1Indication
alarm
load reduction
Gr 2Automatic
start ofstandby pump
with alarm
Gr 3Shutdownwith alarm
Comments
2.0 Servo oil for CP-propeller
Pressure IL, IR, LA AS1) The indicators shall be able to
showsudden peaks in servo pressure.
Level IL, LA
Differential pressure over filter HA 2)
Gr 1 = Sensor(s) for indication, alarm, load reduction (common
sensor permitted but with different set points andalarm shall be
activated before any load reduction)Gr 2 = Sensor for automatic
start of standby pumpGr 3 = Sensor for shutdownIL = Local
indication (presentation of values), in vicinity of the monitored
component
IR = Remote indication (presentation of values), in engine
control room or another centralized control station suchas the
local platform/manoeuvring consoleA = Alarm activated for logical
valueLA = Alarm for low valueHA = Alarm for high valueAS =
Automatic start of standby pump with corresponding alarm
LR = Load reduction, either manual or automatic, with
corresponding alarm, either slow down (r/min reduction)
oralternative means of load reduction (e. g. pitch reduction),
whichever is relevant.
SH = Shut down with corresponding alarm. May be manually
(request for shut down) or automatically executed ifnot explicitly
stated above.
For definitions of Load reduction (LR) and Shut down (SH), see
the Rules for Classification of Ships Ch.1.
1) To be provided when standby pump is required, see [6.3.1].2)
Applies only to propulsion propellers.
6 Arrangement
6.1 General
6.1.1 Bolts and nuts shall be properly secured, see [8.2.3].
6.2 Arrangement of propeller
6.2.1 The arrangement and design of the propeller shall be such
that satisfactory performance is maintainedunder all operating
conditions.
6.2.2 The arrangement of attached free-wheeling propellers shall
be especially considered.
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6.3 Hydraulic system for pitch control
6.3.1 Unless the propeller is intended for auxiliary purposes
only, for single propulsion plants where thepitch-control mechanism
is operated hydraulically, at least two mutually independent,
power-driven pumpsets shall be installed.
6.3.2 For general requirements with respect to hydraulic
systems, see Ch.6 Sec.5 [8.1].
7 Vibration
7.1 General
7.1.1 Not applicable.
8 Installation inspection
8.1 General
8.1.1 Installation of external components shall be carried out
according to the maker’s specifications.
8.2 Fitting of propeller and propeller blades
8.2.1 For fitting of propeller, see Ch.4 Sec.1.
8.2.2 For blade bolt pre-tensioning, see [3.1.1].
8.2.3 The surveyor shall verify that bolts and nuts are properly
secured. In case bolts are fixed by welding, itshall be verified
that only regions with low stress levels are affected.
8.3 Pitch marking
8.3.1 For pitch marking, see [3.1.4].
8.4 Hydraulic piping
8.4.1 Pipes shall have a suitable location and be properly
clamped. Inspection and testing shall be possible.
8.4.2 The hydraulic system shall be flushed after assembly to a
degree of cleanliness as specified by themaker.
8.4.3 System hydraulic oil shall be in accordance with maker's
specification.
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9 Shipboard testing
9.1 Sea trial
9.1.1 For controllable pitch propellers, the pitch function and
the servo pressure shall be demonstrated tothe satisfaction of the
surveyor. Also the function of the local pitch control shall be
demonstrated, and thecorrectness of local pitch indicator shall be
verified.
9.1.2 Unless the propeller is intended for auxiliary purposes
only, the pitch behaviour with inactive servo(zero servo pressure)
shall be demonstrated to the surveyor during sea trial.
9.1.3 The performance of the propeller shall be tested at both
full ahead operation and full astern operation.For fixed pitch
propellers reversing shall be tested at maximum permissible astern
r/min. For controllablepitch propellers reversing shall be tested
at maximum astern pitch of maximum permissible r/min.
9.1.4 For controllable pitch propellers, the function and
setting of the safety valve shall be demonstrated tothe
satisfaction of the surveyor.
9.1.5 The filter for the servo oil shall be inspected after the
sea trial.
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SECTION 2 WATER JETS
1 General
1.1 Application
1.1.1 The rules in this section apply to axial water jets
intended for main propulsion and steering for alltypes of
vessels.
1.1.2 Ch.2 describes all general requirements for rotating
machinery and forms the basis for all sections inCh.3, Ch.4,Ch.5
and Ch.10.
1.1.3 Water jet units with main steering function are also
regarded as steering gear for the vessel.
1.1.4 Water jet units for auxiliary steering purposes (i.e. not
for propulsion) are only subject to classificationafter special
consideration.
1.2 Documentation
1.2.1 The Manufacturer shall submit the documentation required
by Table 1. The documentation shall bereviewed by the Society as a
part of the certification contract.
Table 1 Documentation requirements
Object Documentation type Additional description Info
C020 - Assembly or arrangementdrawing Including cross section
FI
C040 - Design analysis Impeller thrust, vessel thrust andmaximum
reversing forces at crash stop FI
Z100 - SpecificationWater jet pump characteristic, withoperation
limits including cavitation limits,see limit as for Table 5
FIWaterjet, fixed;Waterjet, variable
Z100 - Specification
Normal operating parameters that definethe permissible operating
conditions, suchas thrust, impeller speed, vessel speed,impeller
speed. versus vessel speed, seelimitations in Table 5
FI
Z261 - Test report Non-destructive testing (NDT) FI
C030 - Detailed drawingInput shaft and impeller shaft shallbe
documented according to rules forshafting
AP
C020 - Assembly or arrangementdrawing Bearing arrangement with
particulars. AP
C040 - Design analysis Calculated lifetime of roller bearings
AP
Shafting
C030 - Detailed drawing Seal box, if water lubricated. FI
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Object Documentation type Additional description Info
C030 - Detailed drawingAll bolt connections carrying thrust
ortorque, specification of bolt material andtightening procedure
(bolt pre-stress)
AP
C030 - Detailed drawing Including NDT specification
FIImpeller
C040 - Design analysis Impeller blade strength calculations. FI,
R
C030 - Detailed drawing With guide vanes FIStator housing
C040 - Design analysis Strength calculations FI, R
C030 – Detail drawing Including bolting APStern flange
C040 – Design analysis Strength calculation FI
C020 - Assembly or arrangementdrawing Including water inlet
ducting. FI
C030 - Detailed drawing Cross section of unit. FI
C040 - Design analysis Water inlet ducting, hydrodynamic FI
Waterjet casing
C040 - Design analysis Housing strength calculations, see [2.2]
FI, R
C020 - Assembly or arrangementdrawing Steering arrangement
AP
C040 - Design analysis Strength calculation of the steering
andreversing mechanism APReversing arrangement;Steering
arrangement
S042 - Hydraulic control diagram Including relief valve setting
and alarm listwith set points. AP
Reversing deflectoractuator C030 - Detail drawing AP
Steering deflectoractuator C030 - Detail drawing AP
Control and monitoringsystem
I200 - Control and monitoring systemdocumentation According to
Ch.9 AP
AP = For approval; FI = For information; R = On request
1.2.2 For general requirements for documentation, including
definition of the info codes, see Pt.1 Ch.3 Sec.2.
1.2.3 For a full definition of the documentation types, see Pt.1
Ch.3 Sec.3.
1.3 Certification requirements
1.3.1 Water jet parts, semi-products or materials shall be
certified according to Table 2 and tested accordingto Table 3 and
[3.2].
1.3.2 All piping systems shall be properly flushed, in
accordance with the manufacturer’s specification. Thisshall be
documented by a work certificate.
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Table 2 Certification required
Object Certificatetype Issued byCertificationstandard*
Additional description
Waterjet PC Society
PC Society Required if manufactured by subsupplier
MC ManufacturerImpeller
TR Manufacturer Balancing - See [3.2.4]
Stator housing MC Manufacturer
Impeller housing MC Manufacturer
Shafting MC Manufacturer As required in Ch.4 Sec.1
PC Society Required if manufactured by subsupplierHydraulic
actuators forreversing
MC Manufacturer
Other reversing componentsMCNDT
Manufacturer
PC Society Required if manufactured by subsupplierHydraulic
actuators forsteering
MC Society
Other steering components MC Manufacturer
Bolts TR Manufacturer
Ducting MC Manufacturer If delivered integral with the
waterjet
Control and monitoringsystem PC Society
*Unless otherwise specified the certification standard is the
Society Rules.
1.3.3 For general certification requirements, see Pt.1 Ch.3
Sec.4.
1.3.4 For a definition of the certification types, see Pt.1 Ch.3
Sec.5.
1.3.5 The surveyor shall do visual inspection of parts. Visual
inspection shall include random dimensionalcheck with emphasis on
critical dimensions, tolerances and stress raisers.Manufacturer’s
measurement report shall be presented for main items and shall be
available upon request forminor components.Manufacturer’s survey
report shall be available upon request.
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Table 3 Testing and inspection of components
Ultra-sonic orX-ray testing
Surface crackdetection 3) Pressure testing
Dimensionalinspection
Visualinspection Other
Impeller Manufacturer Manufacturer Society Manufacturer1)
Statorhousing Manufacturer
4) Manufacturer Manufacturer Society
Impellerhousing Manufacturer
4) Manufacturer Manufacturer Society
Shafting According to Ch.4 Sec.1
Hydraulicactuators forreversing andsteering 5)
U-S or surface crack detection(Manufacturer)4)
Society orManufacturer2)
Othersteering andreversingcomponents
Manufacturer4) Manufacturer
Bolts
Ducting whendeliveredintegral withthe water jet
Manufacturer Manufacturer Society
1) See [3.2.4].2) Society for steering hydraulic actuators,
Manufacturer for reversing hydraulic actuators.3) Crack detection
in final condition.4) NDT of welds upon request.5) Hydraulic
actuator includes cylinder, rod, cylinder end eye and rod end
eye.
1.4 Definitions
1.4.1 The following definitions in Table 4 are used in this
Section.
Table 4 Definitions
Term Definition
Ductingwater streaming along the vessel’s bottom and flows into
a duct, leading the water to thewater jet. The duct forms an
integral part of the vessel hull. It is normally manufactured at
thebuilder.
Hydraulic actuators used for either steering or reversing as the
driving force that impose the reversing bucket oracts on the
steering nozzle to create a change in the water flow direction.
Impeller the rotating hub with blades. The impeller is connected
to the shaft. The impeller is usually castin one piece.
Alternatively, the blades are welded onto the hub.
Impeller housing the water jet casing surrounding the
impeller.
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Term Definition
Reversing bucket
for reversing purposes, the water jet incorporates components
that can force its entry intothe water flow thereby turning the
water jet discharge to be thrown somewhat forwards. Thiscreates a
reversing force that acts on the vessel. The flow is either thrown
forwards in an angledirected below the vessel, or to both of the
sides of the water jet. The components used forthis purpose is
denoted a bucket.
Stator housingby leading the water flow through a row of
stationary vanes downstream of the impeller, theswirl added to the
water by the impeller is reduced, and the longitudinal speed of the
waterflow is increased. The vanes are usually formed as an integral
part of the water jet housing.
Steering nozzlethe water flow is lead through a passageway that
can be tilted horizontally in relation to thevessel's longitudinal
axis, thereby changing the direction of the water jet flow. This
creates aturning moment used for steering the vessel.
2 Design
2.1 General
2.1.1 For general design principles for machinery, see Sec.1
[2].
2.1.2 The water jet unit shall be capable of withstanding the
loads imposed by all permissible operatingmodes, including the
condition when the inlet of the suction is blocked.
2.1.3 The stresses in water jet components shall be considered
based on loads due to the worst permissibleoperating conditions,
taking into account:
— Hydrodynamic loads, including varying hydrodynamic loads due
to water flow disturbances introduced e.g.by the ducting or
hull.
— Vessel accelerations versus water jet r/minGuidance note:At
full design speed on a straight course and with the vessel
designated trim, giving the designed water head above the water
intake,harmful impeller cavitation shall not occur. Harmful
cavitation in this context is that cavitation which shall reduce
shafting systemand water jet component lifetime by introducing
vibration or impeller erosion.However, the water jet may be exposed
to operating conditions outside the intended design. Such
situations may occur for instancedue to increased vessel weight,
increased hull resistance, vessel operating at deeper waters etc.
In situations where operation exceedsthe design premises, harmful
impeller cavitation may occur as a consequence of abnormal water
jet flow conditions. This phenomenonhas showed to be of increasing
importance with increasing water jet size.To combat this, the water
jet should be designed with reasonable margin for cavitation, and
care should be taken to avoid vesseloverweight due to e.g. reasons
mentioned in the above. The bigger the water jets are the more
important this advice become.
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2.1.4 The water jet units shall be provided with inspection
facilities for inspection of the shaft and impeller.
2.2 Design of components
2.2.1 The dimensions of the shafts and the shafting components,
including bearings, shall comply with therequirements in Ch.4
Sec.1.
2.2.2 The impeller housing and stator housing shall be designed
against fatigue, considering impeller pulsesand other flow
pulses.
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2.2.3 Steering and reversing mechanisms shall be designed taking
into account the worst permissibleoperational conditions.
2.2.4 The materials used in the hydraulic actuators shall be
suitable for the expected environmentalconditions.
2.2.5 Hydraulic actuators for steering shall comply with the
requirements given in the Ch.10.
2.2.6 Hydraulic actuators for reversing shall comply with the
requirements given in Ch.6 Sec.5 [8]. However,if the hydraulic
system for the reversing actuators is the same as for the steering
system, the design and testpressure for the reversing actuators
shall be the same as for the steering actuators. Higher nominal
stressesmay be accepted for the reversing actuator.
2.2.7 The critical details of the duct and connections to the
hull structure shall be designed against extremeloads occurring
during crash stop and fatigue considerations related to reversing,
steering and impellerpulses.
3 Inspection and testing
3.1 General
3.1.1 The certification principles and the principles of
manufacturing survey arrangements (MSA) aredescribed in Pt.1 Ch.1
Sec.4.Regarding material and testing specifications, see Pt.1
Ch.3.
3.1.2 Welding procedures shall be qualified according to a
recognised standard or Pt.2.
3.2 Testing and inspection of parts
3.2.1 The inspection and testing described in the following are
complementary to Table 3.
3.2.2 The visual inspections by the Society shall include random
dimensional check of vital areas such asflange transition radius,
bolt holes etc., in addition to the main overall dimensions.
3.2.3 Particulars concerning ducting inspections are stated in
[8.1.5].
3.2.4 The impeller shall be statically balanced.Guidance
note:VDI standard no. 2060 Quality class 6.3 or ISO 1940/1 Balance
Guide G6.3 may be used as reference.
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3.3 Assembling
3.3.1 For fitting of the impeller to the shaft, see Ch.4 Sec.1
[2.3] to Ch.4 Sec.1 [2.7].
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4 Workshop testing
4.1 General
4.1.1 Not applicable.
5 Control, alarm, safety functions and indications
5.1 General
5.1.1 Systems shall comply with the requirements in Ch.9.
5.2 Monitoring and bridge control
5.2.1 The monitoring of water jets (for propulsion) shall be in
accordance with Table 5 in regard to:indications, alarms and
requests for slowdown.
Table 5 Control and monitoring of water jets
System/Item
Gr 1Indication
alarm
load reduction
Gr 2Automatic
start of stand-by pump
with alarm
Gr 3Shut downwith alarm
Comment
1.0 Steering
Loss of steering and reversingsignal A, LR Request for slow
down
2.0 Hydraulic oil
Pressure IR, LA, LR Request for slow down
Level in supply tank IL, LA
3.0 Lubricating oil
Temperature IR, HA
Pressure (if forced lubrication) IR, LA, LR Request for slow
down
Level in oil tank (if provided) IL, LA
4.0 Operational limitations1)
The ratio impeller r.p.m versusvessel speed IR, HA, LR Request
for slow down
Maximum permissible vesselacceleration exceeded Indication on
bridge
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System/Item
Gr 1Indication
alarm
load reduction
Gr 2Automatic
start of stand-by pump
with alarm
Gr 3Shut downwith alarm
Comment
Gr 1 = Sensor(s) for indication, alarm, load reduction (common
sensor permitted but with different set points andalarm shall be
activated before any load reduction)Gr 2 = Sensor for automatic
start of standby pumpGr 3 = Sensor for shutdownIL = Local
indication (presentation of values), in vicinity of the monitored
component
IR = Remote indication (presentation of values), in engine
control room or another centralized control station suchas the
local platform/manoeuvring consoleA = Alarm activated for logical
valueLA = Alarm for low valueHA = Alarm for high valueAS =
Automatic start of standby pump with corresponding alarm
LR = Load reduction, either manual or automatic, with
corresponding alarm, either slow down (r/min reduction)
oralternative means of load reduction (e. g. pitch reduction),
whichever is relevant
SH = Shut down with corresponding alarm. May be manually
(request for shut down) or automatically executed ifnot explicitly
stated above.
For definitions of Load reduction (LR) and Shut down (SH), see
Ch.1.
1) These requirements are only valid for water jets with inlet
diameter in excess of 1 000 mm.
5.2.2 Monitoring and bridge control shall also be in compliance
with Ch.9 and Ch.10 Sec.1 [5.5] to Ch.10Sec.1 [5.7].
5.2.3 Frequent corrections in the steering control system, when
the vessel is on straight course, shall beavoided if
practicable.
Guidance note:The actual corrections should be read preferably
by monitoring the control signal. Alternatively, direct
measurements on mechanicalfeedback device from the water jet can be
used.
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6 Arrangement
6.1 General
6.1.1 The installation and arrangement of the water jet unit
with auxiliaries shall comply with themanufacturer’s
specification.
6.1.2 Ship external parts of the water jet shall be protected by
guard rails or other suitable means.
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7 Vibration
7.1 General
7.1.1 For requirements concerning whirling calculations and
shaft alignment specification, see Ch.2.
7.1.2 For requirements concerning torsional vibration
calculations for water jets, see Ch.2.
8 Installation survey
8.1 Surveys
8.1.1 The fastening of the water jet to the hull and the
structural strengthening around the water jet unitwith ducting
shall be carried out in agreement with the approved drawings.
8.1.2 Impeller clearances shall be checked after installation
and shaft alignment and shall be in accordancewith the
manufacturer’s specification.
8.1.3 Normal procedures for shafting apply, see Ch.4 Sec.1
[7].
8.1.4 Thrust bearing axial clearances after installation shall
be verified to be in accordance with themanufacturer specification,
unless verified during assembly of the water jet.
8.1.5 The ducting shall be manufactured in accordance with
drawings and specifications from the waterjet designer. The
surfaces shall be smooth and free from sharp edges or buckling that
could give raise toturbulence in the water flow and thereby
adversely affect water jet operating conditions.
Guidance note:Great care should be taken in assuring that the
ducting dimensions agree with the water jet designer’s drawings.
The ducting designershould be consulted for use of possible
dimensional checking equipment, such as templates especially made
for that purpose.
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8.1.6 Pressure testing of piping shall be done according to
Ch.6.
9 Shipboard testing
9.1 General
9.1.1 For general requirements related to the testing of control
and monitoring, see Ch.9.For testing of steering gear, Ch.10 Sec.1
[9] applies.
9.1.2 Final acceptance of the control system is dependent upon
satisfactory results of the harbour testingand the final sea trial,
as specified in items [9.1.3], [9.1.4] and [9.1.5].
9.1.3 Attention shall be paid to combinations of operational
functions. Testing of all combinations of functionsshall be carried
out.
9.1.4 Indication and alarm (if applicable) of operation outside
the specified operation limits shall be checked.This applies to
acceleration as well as impeller speed versus vessel speed.
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9.1.5 The water jet speed versus vessel speed shall be noted and
plotted against the manufacturersoperational curves when inlet
diameter exceeds 1000 mm. The surveyor shall verify the correct
reading ofvalues, and the results shall be submitted to the
approval centre after completion of test.
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SECTION 3 PODDED AND GEARED THRUSTERS
1 General
1.1 Application
1.1.1 The rules apply to thruster plants intended for
propulsion, propulsion and steering, dynamic positioningand, if
above 300 kW for auxiliary duty. However, the requirements in
[3.2.2], [3.2.3], [5], and [9] apply toall thrusters.The tunnel and
other parts, that are welded or bolted to the hull and form a
barrier against the ingress ofseawater, shall always be subject to
approval, also for auxiliary units of 300 kW or less.Thrusters of
unconventional design are evaluated based on equivalence and may be
accepted provided thatsafety and reliability can be documented to
be equivalent or better than the requirements of this section.
1.1.2 For thrusters that are part of a Dynamic Positioning
System, additional requirements are given in Pt.6Ch.3 Sec.1 and
Pt.6 Ch.3 Sec.2.For thrusters that are installed in a vessel with
additional class notation RP additional requirements are givenin
Pt.6 Ch.2 Sec.7.For thrusters intended for navigation in ice,
additional requirements are given in Pt.6 Ch.6.
1.1.3 Ch.2 describes all general requirements for rotating
machinery and forms the basis for all sections inCh.3, Ch.4 and
Ch.5.
1.1.4 The requirements in [2.4] are specific for steering gear
for azimuth thrusters and replace theequivalent requirements in
Ch.10 Sec.1, which apply to conventional rudders.However, Ch.10
also gives requirements, depending on vessel type and size, which
shall be complied with inaddition to the requirements in [2.4].
1.1.5 For HS, LC and NSC the following rules also apply:
— machinery in general: HSC Code 9.1.1 to 9.1.14, HSC Code 9.7
and 9.8 (passenger craft), and HSC code9.9 (cargo craft)
— propulsion and lift devices: HSC Code 9.6.1 to 9.6.5.
1.2 Definitions1.2.1
Table 1 Definitions
Term Definition
Auxiliary thruster is a thruster for all other purposes than
propulsion and dynamic positioning.
Azimuth thruster is capable of providing omni-directional thrust
by being rotated around the vertical axis.
Declared steering anglelimits
are the operational limits in terms of maximum steering angle,
or equivalent, according tomanufacturer's guidelines for safe
operation, also taking into account the vessel's speed orpropeller
torque/speed or other limitation.
Dynamic positioningthruster
is a thruster that is a part of a dynamic positioning system on
board a vessel with a dynamicpositioning class notations, see Pt.6
Ch.3 Sec.2 and Pt.6 Ch.3 Sec.1.
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Term Definition
Geared thruster thruster with a lower gear or lower and upper
gear.
Podded thruster thruster with the prime mover directly attached
to the propeller shaft (often called “pod orpodded propulsor”).
Propulsion thruster is a thruster that is assigned to propulsion
of the vessel. A propulsion thruster may also providesteering
function.
Thrusteris a unit equipped with a propeller or impeller in order
to produce thrust and is considered to bethe complete assembly;
from the propeller with nozzle (if applicable) to the input shaft
at theupper gear or slip ring unit (if applicable).
Tunnel thruster thruster mounted in a tunnel for the purpose of
providing lateral thrust for the vessel
1.3 Documentation
1.3.1 Documentation shall be submitted as required by Table
2.
Table 2 Documentation requirements
Object Documentation type Additional description Info
C020 - Assembly orarrangement drawing
Arrangement drawing of the thruster unit, including driver
andintermediate shafting (yard supply) AP
C020 - Assembly orarrangement drawing
Sectional drawing of the whole thruster unit, including
bearingarrangement AP
C020 - Assembly orarrangement drawing Shaft brake/locking device
arrangement (if applicable) FI
C040 - Design analysis Shaft brake/locking device capacity
calculation (if applicable) FI
C020 - Assembly orarrangement drawing Sealing arrangement for
flexibly mounted tunnel thrusters AP
C030 - Detaileddrawing
Sectional drawings including all torque transmitting parts, e.g.
shafts,couplings and gears AP
C030 - Detaileddrawing
For podded thrusters: sectional drawing of electric motor
includingparticulars of stator-to-housing and rotor-to-shaft
connections anddefined air gap with tolerances
AP
C040 - Design analysis Component strength calculation for
structural parts FI, R
C040 - Design analysis Torsional vibration calculations (yard
supply), see Ch.2 Sec.2 AP
C040 - Design analysis Torsional impact calculations. Applicable
if high transient torque inelectric motor drive (e.g. star-delta
start), (yard supply), see Ch.2 Sec.2 AP, R
C040 - Design analysis Bearing life time calculations.
Applicable if roller bearings FI
Z100 – Specification Material, nominal surface pressure and
clearance tolerances in case offluid film bearings. Applicable if
plain bearings FI
Thruster
C040 - Design analysis For podded thrusters: heat balance
calculation FI
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Object Documentation type Additional description Info
S010 - Piping diagram(PD) For podded thrusters: bilge system
AP
Z060 – Functionaldescription For podded thrusters: bilge system
FI
Z030 –Arrangementplan Steering gear compartment for propulsion
thrusters (yard supply) FI
Z050 - Designphilosophy
Operational (design) limitations such as, but not limited
to:
— limitations in rotation of azimuth thrusters at high vessel
speed— maximum vessel speed for lowering and lifting of retractable
units
FI
Z051 - Design basis Maximum forces acting on the thruster unit
under the most extremeallowable manoeuvre, including crash stop
FI
Z060 – Functionaldescription
Load control system including description of the method used to
controlthe load (CP-mechanism, frequency converter etc.). FI, R
Z100 – Specification Specification of torque capacity of
off-the-shelf gear transmissions usedin steering motor arrangements
(see footnote in [1.4.4]) FI
Z161 - Operationmanual
Operation instruction poster for control and steering of the
thruster,including emergency operation. Shall be displayed on the
navigationbridge and in the steering gear compartment
AP
Z250 – Procedure Assembling and adjustment procedures regarding
gear mesh contact fordrive gears and steering gears FI, R
Z250 – Procedure For propulsion thrusters: Crash stop procedure
FI
Z051 - Design basis
Maximum start-up torque (KAP factor, see Class Guideline
DNVGL-CG-0036).Does not apply to thrusters which obtain the
required scuffing safetyfactor (see Table 3) with a peak torque
factor KAP of 1.5 or higher andhave equivalent mass moment of
inertia of motor higher than equivalentmass moment of inertia of
the propeller
FI
C030 - Detaileddrawing Sectional drawings of slewing bearing and
thruster support bearing AP
Fixationarrangement
Housing andstructuralpart
C030 - Detaileddrawing
Structural drawings (gear housing etc.) and connections to the
tunnel ornozzle (if not covered by sectional drawings), including
NDT specification AP
Gears Ref to Ch.4 Sec.2 AP
Propeller Ref to Sec.1 AP
Propellershaft seal
C030 - Detaileddrawing AP
Propellernozzle
C030 - Detaileddrawing AP
Steeringcolumn
C030 - Detaileddrawing Including NDT specification AP
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Object Documentation type Additional description Info
C020 - Assembly orarrangement drawing Steering gear assembly,
including azimuth brake/locking device AP
C030 - Detaileddrawing Including all load transmitting parts
AP
S042 - Hydrauliccontrol diagram Including alarm and indicator
set points AP
Z060 – Functionaldescription
Description of steering gear function and load limiting devices
includingmaximum values FI
Z100 – Specification Load data for azimuth gear, including
capacity of azimuth brake. FI
Z110 – Data sheetElectrical motor for steering gear (if
applicable), including motor ratingaccording to IEC and torque
versus speed characteristics of electricalmotor
FI, R
Steeringgearactuator
Z110 – Data sheet Frequency converter set value of parameters,
list of alarms, shutdownsand ramp functions. (if applicable) FI
Thruster seal C030 - Detaileddrawing Sealing arrangement for
steering column, see [2.5] AP
Lubricatingsystem
S010 - Piping diagram(PD) Lubrication oil system including alarm
and indicator set points AP
Control andmonitoringsystem
I200 - Control andmonitoring systemdocumentation
AP
AP = For approval; FI = For information; R = On request
1.3.2 For general requirements for documentation, including
definition of the info codes, see Pt.1 Ch.3 Sec.2.
1.3.3 For a full definition of the documentation types, see Pt.1
Ch.3 Sec.3.
1.4 Certification requirements
1.4.1 The complete thruster shall be delivered with certificate
as required in Table 3 and tested andinspected as required in Table
2. It shall be based on the design approval in [2], the component
certificationin [3], the workshop testing in Table 4[4]and relevant
monitoring equipment in [5].
Table 3 Certification requirements
Object Certificatetype
Issued by Certificationstandard*
Additional description
Thruster PC Society Complete thruster
Underwater housing MC Manufacturer
Inboard housing MC Manufacturer
Outer housing MC Society Non rotating, forming barrier to
sea
Steering column or rotatingsupport
MC Society
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Object Certificatetype
Issued by Certificationstandard*
Additional description
Propeller nozzle MC Society
Control and monitoringsystems
PC Society — Required for thrusters forpropulsion and
dynamicpositioning duty
*Unless otherwise specified the certification standard is the
Society rules.
Table 4 Testing and inspection of components
Ultra-sonic orX-ray testing
Surface crackdetection 2) Pressure testing
Dimensionalinspection
Visualinspection Other
Underwaterhousing Manufacturer Society
Inboardhousing Manufacturer Society
Outerhousing Manufacturer Society
Propellernozzle Manufacturer Society
Steeringcolumn orrotatingsupport
Manufacturer1) Manufacturer Society
1) The test certificate shall refer to a recognized standard and
approved acceptance levels.2) Surface and crack detection (MPI or
dye penetrant) is required in way of zones with stress risers and
in welded
connections. The extent and acceptance criteria shall be
specified in the documentation submitted for approval.
1.4.2 For general certification requirements, see Pt.1 Ch.3
Sec.4.
1.4.3 For a definition of the certification types, see Pt.1 Ch.3
Sec.5.
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1.4.4 Certification requirements are given in the respective
references or in this section:
— pinions and wheels for propeller drive, see Ch.4 Sec.2—
pinions and wheels for azimuth steering, see Ch.4 Sec.2*
Guidance note:* For propulsion thrusters which have high speed
hydraulic motor or electric motor (equivalent to rudder actuator)
which iscombined with “off the shelf”, mass produced gear boxes,
the certification of the gearboxes may be based on function
testingonly, provided that:
— vessel has two or more independent propulsion thrusters
— vessel is fully manoeuvrable with one thruster locked in worst
possible condition (other thruster(s) in operation)
— each thruster is provided with two or more steering gear
actuators
— the gearboxes shall be conservatively chosen with regard to
required safety factors and able to handle all relevant loads
forthe steering gear
— easily replaceable.
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— shafts, see Ch.4 Sec.1— clutches, see Ch.4 Sec.3— couplings,
see Ch.4 Sec.4— propeller, see Sec.1— hydraulic motor for steering
(to be handled as a pump), see Ch.6 Sec.6.
1.4.5 Electrical equipment shall be certified as required in
Ch.8.
1.4.6 For a definition of the certificate types, see Pt.1
Ch.3
1.4.7 Welds in any part mentioned in [1.4.1], if specified
during approval shall be ultrasonic tested. Thesetests shall be
carried out at an appropriate stage of the manufacturing process.
The test certificate shall referto a recognized standard and
approved acceptance levels.
1.4.8 Visual inspection shall be carried out of all parts
mentioned in Table 4 and [1.4.4] unless otherwisedefined in a
manufacturing survey arrangements (MSA).
1.4.9 Ancillaries, which are not part of the steering gear, such
as pumps, electric motors, coolers, piping,filters and valves that
are delivered as integral parts of the lubrication, hydraulic
operation and coolingsystems of the thruster, shall be subjected to
a quality control in accordance with the thruster
manufacturer’squality system as found relevant.
2 Design
2.1 General
2.1.1 The thruster shall be capable of withstanding the loads
imposed by all allowable operating conditionsincluding effects of
thermal expansion elastic deformations.
2.1.2 In-dock inspection of thruster gears shall be made
possible either through proper inspection openings,or by other
means (e.g. fibre optical instruments) without extensive
dismantling.
2.1.3 Podded thruster internals shall be shielded in order to
provide safe entrance/accessibility to performnecessary maintenance
and inspection without risk of damage neither to equipment nor
personnel. Sufficientventilation shall be provided.
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2.1.4 For general design requirements for piping and ancillary
equipment such as pipes, pumps, filters andcoolers, see Ch.6 and
Ch.7, as found applicable.Hydraulic components shall be chosen in
consideration of the expected level of contamination the system
willbe exposed to during its lifetime.Flange connections for piping
systems shall be located as far as practicable outside the podded
thruster.Flanges and valves inside podded thrusters shall be
arranged to minimise the consequence of leakage, i.e. bydrip trays
and leakage drain to safe location.
2.1.5 The cooling system shall be in accordance with Ch.6 Sec.5
[2].
2.1.6 For design and arrangement requirements for electric
systems and control systems reference is madeto Ch.10 Sec.1 [5]
(for propulsion thrusters only) and Ch.8 and Ch.9.
2.2 Shafting
2.2.1 The dimensions of the shafts and the shafting components
shall be in accordance with Ch.4 Sec.1.For podded thrusters there
shall be a sufficient air gap between rotor and stator under all
relevant operatingconditions.
2.2.2 A shaft sealing box shall be installed to prevent water
from entering into internal parts of the thrusteror into the ship.
The sealing arrangement shall protect the steel shafts from
seawater, unless corrosion-resistant steel especially approved by
the Society is used.For single thruster arrangements, the shaft
seal shall be duplicated and means for leakage detection shall
beprovided.
2.3 Gear transmissions
2.3.1 Gear transmissions shall be in accordance with the
requirements in Ch.4 Sec.2 as far as applicable.The lifetime
criteria given in Table 5 shall as a minimum be used for
dimensioning the gears in the propellerdrive line.
Table 5 Thruster type and load cycles
Type of thruster Minimum number of input shaft revolutions at
full power(NL load cycles)
Propulsion 1) 1·1010
Dynamic positioning 5·108
Auxiliary 5·107
1) For thrusters subject to frequent overload (intermittent
load), relevant load and corresponding accumulated numberof load
cycles shall be applied, see also Ch.2 Sec.1 [2].
The safety factors SF, SH, SHSS and SS shall be at least as
specified in Ch.4 Sec.2 Table 5. The safety factorsfor gears in
thrusters for dynamic positioning shall be as for propulsion
gears.
2.4 Azimuth steering gear for thrusters
2.4.1 Steering gear for auxiliary and dynamic positioning
thrusters need not comply with [2.4.2], [2.4.3],[2.4.4], [2.4.5],
[2.4.7], requirements for safety valve set value in [2.4.8],
[2.4.10] and [2.4.17].
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2.4.2 Steering arrangement for the vessel shall comply with the
following requirements:
a) the vessel shall be provided with two steering gears, each
with strength and capacity as specified belowb) a single failure
shall neither lead to loss of steering of the vessel, nor
consequential damage to the
thrusters.
2.4.3 The steering gear for the thruster shall:
a) be capable of operating the thruster for the purpose of
steering the vessel at maximum ahead servicespeed, which shall be
demonstrated at sea trial
b) have capacity to turn the thruster from side to side
according to steering gear test. See Ch.10 Sec.1[2.4.1] b.
c) be capable of bringing the thrusters back to neutral position
from any allowable angle at maximumservice speed.
2.4.4 The thrusters shall be prevented from sudden turning in
the case of power failure, failure in thesteering control system or
any other single failure, except failure in steering column and
support bearings.
2.4.5 It shall be possible to bring the thruster to neutral
position and lock it to allow it to produce thrust inthe case that
its steering gear is inoperative.
2.4.6 Steering gear shall be designed considering all relevant
loads from internal and external forces.
2.4.7 Steering gear drivers shall be designed with a capacity
not less than 125% of the maximum torqueoccurring during the
steering gear test as described in Ch.10 Sec.1 [2.4.1] b). See also
[2.4.17] for electromotor rating.
2.4.8 The steering gear arrangement shall be provided with a
load limiting device (limiting torque/ pressureas applicable), such
as relief valve or frequency converter limiter.The load limiting
device shall have a set value not less than 125% of torque
occurring during steering geartes